Neural correlates of auditory distraction revealed in theta-band EEG

Selective attention involves the exclusion of irrelevant information in order to optimize perception of a single source of sensory input; failure to do so often results in the familiar phenomenon of distraction. The term ‘distraction’ broadly refers to a perceptual phenomenon. In the present study we attempted to find the electrophysiological correlates of distraction using an auditory discrimination task. EEG and event-related potential responses to identical stimuli were compared under two levels of distraction (continuous broad-band noise or continuous speech). Relative to broad-band noise, the presence of a continuous speech signal in the unattended ear impaired task performance and also attenuated the N1 peak evoked by nontarget stimuli in the attended ear. As the magnitude of a peak in the event-related potential waveform can be modulated by differences in intertrial power but also by differences in the stability of EEG phase across trials, we sought to characterize the effect of distraction on intertrial power and intertrial phase locking around the latency of the N1. The presence of continuous speech resulted in a prominent reduction of theta EEG band intertrial phase locking around the latency of the N1. This suggests that distraction may act not only to disrupt a sensory gain mechanism but also to disrupt the temporal fidelity with which the brain responds to stimulus events.